Analysis of a Destructive Wind Storm on 16 November 2008 in Brisbane, Australia

Journal Article · Mon Aug 25 00:00:00 EDT 2014 · Monthly Weather Review

DOI:https://doi.org/10.1175/MWR-D-13-00405.1· OSTI ID:1395023

Richter, Harald ^[1]; Peter, Justin ^[1]; Collis, Scott ^[2]

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1. Bureau of Meteorology, Melbourne, VIC (Australia). Centre for Australian Weather and Climate Research
2. Argonne National Lab. (ANL), Argonne, IL (United States). Environmental Science Division

During the late afternoon on 16 November 2008 the Brisbane (Australia) suburb of “The Gap” experienced extensive wind damage caused by an intense local thunderstorm. The CP2 research radar nearby detected near-surface radial velocities exceeding 44 m s^-1 above The Gap while hail size reports did not exceed golf ball size, and no tornadoes were reported. This study shows that the storm environment was characterized by a layer of very moist (mixing ratios exceeding 12 g kg^-1) near-surface air embedded in strong storm-relative low-level flow, whereas the storm-relative winds aloft were significantly weaker. And while the thermodynamic storm environment contained a range of downdraft promoting ingredients such as a ~4 km high melting level above a ~2 km deep layer with nearly dry adiabatic lapse rates mostly collocated with dry ambient air, a ~1 km deep stable layer near the ground would generally lower expectations of destructive surface winds based on the downburst mechanism. We also found that once observed reflectivities exceed 70 dBZ that downdraft cooling due to hail melting and downdraft acceleration based on hail loading are likely to become non-negligible forcing mechanisms for a strong downdraft. The study found a close proximity of the hydrostatically and dynamically driven mesohigh at the base of the downdraft to a dynamically driven mesolow associated with a radar-observed low-level circulation. This proximity is hypothesized to have been instrumental in the observed anisotropic horizontal acceleration of the near-ground outflow and the ultimate strength of the Gap storm surface winds. Finally, we speculate that the 44 weak storm-relative midlevel winds allowed the downdraft to descend close to the low45 level circulation which set up this strong horizontal perturbation pressure gradient.

• Research Organization: Argonne National Laboratory (ANL), Argonne, IL (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Biological and Environmental Research (BER); Centre for Australian Weather and Climate Research (CAWCR), Australian Bureau of Meterology
• Grant/Contract Number: AC02-06CH11357
• OSTI ID: 1395023
• Journal Information: Monthly Weather Review, Vol. 142, Issue 9; ISSN 0027-0644
• Publisher: American Meteorological Society
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
58 GEOSCIENCES
buoyancy
cold pools
downbursts
hail
mesocyclones
radars/radar observations